Bacillus cereus produces an exo-enterotoxin in semi-defined media which is also totally dialyzable thereby facilitating purification efforts. This toxin may be purified by ammonium sulfate precipitation, gel filtration and ion exchange chromatography. The toxin is devoid of phospholipolytic activity and may be detected by skin tests in guinea pigs or rabbits. The toxin is lethal to mice and causes a diarrheal response in Rhesus monkeys.